In cell retrieval processing, a cell list is acquired from a library, a classification file corresponding to the cell list is read to display a classification screen of setting a cell retrieval condition, and a cell satisfying the retrieval condition set through the classification screen is retrieved from the cell list. In logic diagram rendering processing, a location name described as an instance name in an HDL file is decoded, and a location attribute indicative of a location on the diagram is added to an instance to render a logic diagram. In instance arrangement processing, a location name indicative of an arrangement location on the diagram is set as an instance name for rendering. In instance movement processing, the instance name of an instance is changed to a location name indicative of a specified movement location for rendering. In attribute display processing, attributes of pins and nets are read for display nearby.